In vehicular transport and traffic management, it is known to use Intelligent Transport System (ITS) applications for supporting drivers. In this way, traffic safety can be improved by providing the drivers with information which allows for making smarter decisions. Such ITS applications may involve transmitting information between different vehicles, e.g., in the form of a Cooperative Awareness Message (CAM). The information may be used for providing a warning or guidance to the driver, e.g., in the form of an emergency vehicle warning, an intersection collision warning, a slow vehicle warning, or a motorcycle approaching indication. The information may be transmitted using a radio technology for vehicle-to-vehicle (V2V) communication, e.g., as specified by the IEEE 802.11p standard, also referred to as WAVE (Wireless Access in Vehicular Environments). According to the IEEE 802.11p standard, a wireless ad-hoc network may be formed between different vehicles.
CAMs are messages which are typically periodically broadcast by a vehicle to inform nearby vehicles about the current status of the vehicle. CAMs may for example be used for transmitting the current geographical position, speed, and/or basic attributes of the vehicle. A vehicle may receive CAMs from other vehicles and utilize the information provided in the CAMs for supporting its operator, e.g., by providing a warning or other guidance.
More details on CAMs can be found in ETSI TS 102 637-3 “Intelligent Transport Systems (ITS); Vehicular Communications; Basic Set of Applications; Part 2: Specification of Cooperative Awareness Basic Service”. Here, a generation of cooperative applications is described, which are based on the IEEE 802.11p specifications. The traffic model for the transmission of such CAM messages is specified to use periodic broadcast traffic consisting of approx. 500 payload bytes with a repetition rate 5-10 Hz and event-driven broadcast traffic consisting of approx. 500 payload bytes. Both traffic types may exist at the same time.
The ad-hoc network according to IEEE 802.11p is a contention based system, in which different V2V communication devices compete for access to the same radio channel. Accordingly, there is also a risk of colliding access attempts by different V2V communication devices. Such collisions may in turn result in delays until a V2V communication device successfully gains access to the radio channel.
Accordingly, there is a need for techniques which allow for achieving reliable and low latency V2V communication.